#!/usr/bin/env python3
#
# Copyright 2012 Free Software Foundation, Inc.
#
# This file is part of GNU Radio
#
# GNU Radio is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3, or (at your option)
# any later version.
#
# GNU Radio is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with GNU Radio; see the file COPYING.  If not, write to
# the Free Software Foundation, Inc., 51 Franklin Street,
# Boston, MA 02110-1301, USA.
#

import osmosdr
from gnuradio import blocks
from gnuradio import gr
from gnuradio import eng_notation
from gnuradio.fft import window
from gnuradio.eng_option import eng_option
from optparse import OptionParser
from functools import partial

import sys
import signal
import time
import datetime

try:
    from PyQt5 import Qt
    from gnuradio import qtgui
    import sip
    from gnuradio.qtgui import Range, RangeWidget
except ImportError:
    sys.stderr.write("Error importing GNU Radio's Qtgui.\n")
    sys.exit(1)


class CallEvent(Qt.QEvent):
    """An event containing a request for a function call."""
    EVENT_TYPE = Qt.QEvent.Type(Qt.QEvent.registerEventType())

    def __init__(self, fn, *args, **kwargs):
        Qt.QEvent.__init__(self, self.EVENT_TYPE)
        self.fn = fn
        self.args = args
        self.kwargs = kwargs


class freq_recv(gr.sync_block, Qt.QObject):
    def __init__(self, callback):
        gr.sync_block.__init__(self, name="freq_recv", in_sig=None, out_sig=None)
        Qt.QObject.__init__(self)

        self.set_freq=callback

        # Advertise 'msg' port
        self.message_port_register_in(gr.pmt.intern('msg'))
        self.set_msg_handler(gr.pmt.intern('msg'), self.handle_msg)

    def handle_msg(self, msg_pmt):
        # Unpack message & call set_freq on main thread
        meta = gr.pmt.to_python(gr.pmt.car(msg_pmt))
        msg = gr.pmt.cdr(msg_pmt)
        if meta=="freq":
            freq = gr.pmt.to_double(msg)
            Qt.QCoreApplication.postEvent(self, CallEvent(self.set_freq, freq))

    def event(self, event):
        event.accept()
        result = event.fn(*event.args, **event.kwargs)
        return True


class app_top_block(gr.top_block, Qt.QMainWindow):
    def __init__(self, argv, title):
        gr.top_block.__init__(self, title)
        Qt.QMainWindow.__init__(self)
        self.setWindowTitle(title)

        parser = OptionParser(option_class=eng_option)
        parser.add_option("-a", "--args", type="string", default="",
                          help="Device args, [default=%default]")
        parser.add_option("-A", "--antenna", type="string", default=None,
                          help="Select RX antenna where appropriate")
        parser.add_option("", "--clock-source",
                          help="Set the clock source; typically 'internal', 'external', 'external_1pps', 'mimo' or 'gpsdo'")
        parser.add_option("-s", "--samp-rate", type="eng_float", default=None,
                          help="Set sample rate (bandwidth), minimum by default")
        parser.add_option("-f", "--center-freq", type="eng_float", default=None,
                          help="Set frequency to FREQ", metavar="FREQ")
        parser.add_option("-c", "--freq-corr", type="eng_float", default=None,
                          help="Set frequency correction (ppm)")
        parser.add_option("-g", "--gain", type="eng_float", default=None,
                          help="Set gain in dB (default is midpoint)")
        parser.add_option("-G", "--gains", type="string", default=None,
                          help="Set named gain in dB, name:gain,name:gain,...")
        parser.add_option("-r", "--record", type="string", default="/tmp/name-f%F-s%S-t%T.cfile",
                          help="Filename to record to, available wildcards: %S: sample rate, %F: center frequency, %T: timestamp, Example: /tmp/name-f%F-s%S-t%T.cfile")
        parser.add_option("", "--dc-offset-mode", type="int", default=None,
                          help="Set the RX frontend DC offset correction mode")
        parser.add_option("", "--iq-balance-mode", type="int", default=None,
                          help="Set the RX frontend IQ imbalance correction mode")
        parser.add_option("-W", "--waterfall", action="store_true", default=False,
                          help="Enable waterfall display")
        parser.add_option("-F", "--fosphor", action="store_true", default=False,
                          help="Enable fosphor display")
        parser.add_option("-S", "--oscilloscope", action="store_true", default=False,
                          help="Enable oscilloscope display")
        parser.add_option("-Q", "--qtgui", action="store_true", default=False,
                          help="Enable QTgui 'all-in-one' display")
        parser.add_option("", "--avg-alpha", type="eng_float", default=1e-1,
                          help="Set fftsink averaging factor, default=[%default]")
        parser.add_option("", "--averaging", action="store_true", default=False,
                          help="Enable fftsink averaging, default=[%default]")
        parser.add_option("", "--peak-hold", action="store_true", default=False,
                          help="Enable fftsink peak hold, default=[%default]")
        parser.add_option("", "--ref-scale", type="eng_float", default=1.0,
                          help="Set dBFS=0dB input value, default=[%default]")
        parser.add_option("", "--fft-size", type="int", default=1024,
                          help="Set number of FFT bins [default=%default]")
        parser.add_option("", "--fft-rate", type="int", default=30,
                          help="Set FFT update rate, [default=%default]")
        parser.add_option("-v", "--verbose", action="store_true", default=False,
                          help="Use verbose console output [default=%default]")

        (options, args) = parser.parse_args()
        if len(args) != 0:
            parser.print_help()
            sys.exit(1)
        self.options = options

        self._verbose = options.verbose

        try:
            self.src = osmosdr.source(options.args)
        except RuntimeError:
            print("Couldn't instanciate source (no device present?).", file=sys.stderr)
            sys.exit(1)

        try:
            self.src.get_sample_rates().start()
        except RuntimeError:
            print("Source has no sample rates (wrong device arguments?).", file=sys.stderr)
            sys.exit(1)

        # Set the antenna
        if options.antenna:
            self.src.set_antenna(options.antenna)

        # Set the clock source:
        if options.clock_source is not None:
            self.src.set_clock_source(options.clock_source)

        if options.samp_rate is None:
            options.samp_rate = self.src.get_sample_rates().start()

        if options.gain is None:
            gain = self.src.get_gain()
            if gain is None:
                # if no gain was specified, use the mid-point in dB
                r = self.src.get_gain_range()
                try: # empty gain range returned in file= mode
                    options.gain = float(r.start()+r.stop())/2
                except RuntimeError:
                    options.gain = 0
            else:
                options.gain = gain

        self.src.set_gain(options.gain)

        if self._verbose:
            gain_names = self.src.get_gain_names()
            for name in gain_names:
                rg = self.src.get_gain_range(name)
                print("%s gain range: start %g stop %g step %g" % (name, rg.start(), rg.stop(), rg.step()))

        if options.gains:
            for tuple in options.gains.split(","):
                name, gain = tuple.split(":")
                gain = int(gain)
                print("Setting gain %s to %g." % (name, gain))
                self.src.set_gain(gain, name)

        if self._verbose:
            rates = self.src.get_sample_rates()
            print('Supported sample rates %.10g-%.10g step %.10g.' % (rates.start(), rates.stop(), rates.step()))

        self.bandwidth_ok = True
        try:
            rg = self.src.get_bandwidth_range()
            range_start = rg.start()
            if self._verbose:
                print('Supported bandwidth rates %.10g-%.10g step %.10g.' % (rg.start(), rg.stop(), rg.step()))
        except RuntimeError as ex:
            self.bandwidth_ok = False

        if options.center_freq is None:
            freq = self.src.get_center_freq()
            if freq != 0:
                options.center_freq = freq
            else:
                # if no freq was specified, use the mid-point in Hz
                r = self.src.get_freq_range()
                options.center_freq = float(r.start()+r.stop())/2
                if self._verbose:
                    print("Using auto-calculated mid-point frequency")

        input_rate = self.src.set_sample_rate(options.samp_rate)
        self.src.set_bandwidth(input_rate)

        if self._verbose:
            ranges = self.src.get_freq_range()
            print("Supported frequencies %s-%s"%(eng_notation.num_to_str(ranges.start()), eng_notation.num_to_str(ranges.stop())))


            for name in self.src.get_gain_names():
                print("GAIN(%s): %g"%(name, self.src.get_gain(name)))

        # initialize values from options
        if options.freq_corr is not None:
            self.set_freq_corr(options.freq_corr)

        self.dc_offset_mode = options.dc_offset_mode
        self.iq_balance_mode = options.iq_balance_mode

        # initialize reasonable defaults for DC / IQ correction
        self.dc_offset_real = 0
        self.dc_offset_imag = 0
        self.iq_balance_mag = 0
        self.iq_balance_pha = 0

        # see https://github.com/gnuradio/gnuradio/issues/5175 - 3.9 has a backport of pyqwidget, but 3.10 does not.
        check_qwidget = lambda : self.scope.pyqwidget() if "pyqwidget" in dir(self.scope) else self.scope.qwidget()

        if options.fosphor:
            from gnuradio import fosphor
            self.scope = fosphor.qt_sink_c()
            self.scope.set_frequency_range(0, input_rate)
            self.scope_win = sip.wrapinstance(check_qwidget(), Qt.QWidget)
            self.scope_win.setMinimumSize(800, 300)
        elif options.waterfall:
            self.scope = qtgui.waterfall_sink_c(
                options.fft_size,
                wintype=window.WIN_BLACKMAN_hARRIS,
                fc=0,
                bw=input_rate,
                name="",
                nconnections=1
            )
            self.scope.enable_grid(False)
            self.scope.enable_axis_labels(True)
            self.scope.set_intensity_range(-100, 20)
            self.scope_win = sip.wrapinstance(check_qwidget(), Qt.QWidget)
            self.scope_win.setMinimumSize(800, 420)

        elif options.oscilloscope:
            self.scope = qtgui.time_sink_c(
                options.fft_size,
                samp_rate=input_rate,
                name="",
                nconnections=1
            )
            self.scope_win = sip.wrapinstance(check_qwidget(), Qt.QWidget)
            self.scope_win.setMinimumSize(800, 600)

        elif options.qtgui:
            self.scope = qtgui.sink_c(
                options.fft_size,
                wintype=window.WIN_BLACKMAN_hARRIS,
                fc=0,
                bw=input_rate,
                name="",
                plotfreq=True,
                plotwaterfall=True,
                plottime=True,
                plotconst=True
            )
            self.scope_win = sip.wrapinstance(check_qwidget(), Qt.QWidget)
            self.scope.set_update_time(1.0/10)
            self.scope_win.setMinimumSize(800, 600)

        else:
            self.scope = qtgui.freq_sink_c(
                fftsize=options.fft_size,
                wintype=window.WIN_BLACKMAN_hARRIS,
                fc=0,
                bw=input_rate,
                name="",
                nconnections=1
            )
            self.scope_win = sip.wrapinstance(check_qwidget(), Qt.QWidget)
            self.scope.disable_legend()
            self.scope_win.setMinimumSize(800, 420)

        self.connect((self.src, 0), (self.scope, 0))
        try:
            self.freq = freq_recv(self.set_freq)
            self.msg_connect((self.scope, 'freq'), (self.freq, 'msg'))
        except RuntimeError:
            self.freq = None

        self.file_sink = blocks.file_sink(gr.sizeof_gr_complex, "/dev/null", False)
        self.file_sink.set_unbuffered(False)
        self.file_sink.close() # close the sink immediately
        # lock/connect/unlock at record button event did not work, so we leave it connected at all times
        self.connect(self.src, self.file_sink)

        self._build_gui()

        # set initial values
        if not self.set_freq(options.center_freq):
            self._set_status_msg("Failed to set initial frequency")
        if options.record is not None:
            self._fre.insert(options.record)

    def record_to_filename(self):
        s = self._fre.text()
        s = s.replace('%S', '%e' % self.src.get_sample_rate())
        s = s.replace('%F', '%e' % self.src.get_center_freq())
        s = s.replace('%T', datetime.datetime.now().astimezone().strftime('%Y%m%d%H%M%S%z'))
        return s

    def _set_status_msg(self, msg, timeout=0):
        self.status.showMessage(msg, timeout)

    def _shrink(self, widget):
        """Try to shrink RangeWidget by removing unnecessary margins"""
        try:
            widget.layout().setContentsMargins(0, 0, 0, 0)
            widget.children()[0].layout().setContentsMargins(0, 0, 0, 0)
        except:
            pass

    def _add_section(self, text, layout):
        """Add a section header to the GUI"""
        frame = Qt.QWidget()
        frame_layout = Qt.QHBoxLayout()
        frame_layout.setContentsMargins(0, 0, 0, 0)
        frame.setLayout(frame_layout)

        wid = Qt.QLabel()
        wid.setText(text)
        wid.setStyleSheet("font-weight: bold;")
        frame_layout.addWidget(wid)
        wid = Qt.QFrame()
        wid.setFrameShape(Qt.QFrame.HLine)
        frame_layout.addWidget(wid)
        frame_layout.setStretchFactor(wid, 1)

        layout.addWidget(frame)

    def _chooser(self, names, callback, default=0):
        """A simple radio-button chooser"""
        buttons = Qt.QWidget()
        blayout = Qt.QHBoxLayout()
        bgroup = Qt.QButtonGroup()
        buttons.setObjectName("foo")
        buttons.setStyleSheet("QWidget#foo {border: 1px outset grey;}")
        buttons.setLayout(blayout)
        chooser = []
        for (num, txt) in enumerate(names):
            rb = Qt.QRadioButton(txt)
            rb.clicked.connect(partial(callback, num))
            chooser.append(rb)
            bgroup.addButton(rb,num)
            blayout.addWidget(rb)
            if num == default:
                rb.setChecked(True)
        return buttons

    def _build_gui(self):

        self.top_widget = Qt.QWidget()

        self.top_layout = Qt.QVBoxLayout(self.top_widget)
        self.top_layout.addWidget(self.scope_win)

        self.setCentralWidget(self.top_widget)

        self.status = Qt.QStatusBar()
        self.setStatusBar(self.status)
        self.status.setStyleSheet("QStatusBar{border-top: 1px outset grey;}")

        if hasattr(RangeWidget, 'EngSlider'):
            eng_widget="eng_slider"
        else:
            eng_widget="counter_slider"

        ##################################################
        # Frequency controls
        ##################################################
        self._add_section("Frequency", self.top_layout)

        r = self.src.get_freq_range()
        self._fr = Range(r.start(), r.stop(), (r.start()+r.stop())/100, self.src.get_center_freq(), 200)
        self._fw = RangeWidget(self._fr, self.set_freq, 'Center Frequency (Hz)', eng_widget, float)
        self._shrink(self._fw)
        self.top_layout.addWidget(self._fw)

        if hasattr(self, 'ppm') and self.ppm is not None:
            self._fcr = Range(-100, 100, 0.1, self.src.get_freq_corr(), 200)
            self._fcw = RangeWidget(self._fcr, self.set_freq_corr, 'Freq. Correction (ppm)', "counter_slider", float)
            self._shrink(self._fcw)
            self.top_layout.addWidget(self._fcw)

        ##################################################
        # Gain controls
        ##################################################
        self._add_section("Gains", self.top_layout)

        self._gr={}
        self._gw={}
        for gain_name in self.src.get_gain_names():
            rg = self.src.get_gain_range(gain_name)
            self._gr[gain_name] = Range(rg.start(), rg.stop(), rg.step(), self.src.get_gain(gain_name), 100)
            self._gw[gain_name] = RangeWidget(self._gr[gain_name], partial(self.set_named_gain,name=gain_name), '%s Gain (dB):'%gain_name, "counter_slider", float)
            self._shrink(self._gw[gain_name])
            self._gw[gain_name].d_widget.counter.setDecimals(2)
            self.top_layout.addWidget(self._gw[gain_name])

        ##################################################
        # Bandwidth controls
        ##################################################
        if self.bandwidth_ok:
            self._add_section("Bandwidth", self.top_layout)

            r = self.src.get_bandwidth_range()
            self._bwr = Range(r.start(), r.stop(), r.step() or (r.stop() - r.start())/100, self.src.get_bandwidth(), 100)
            self._bww = RangeWidget(self._bwr, self.set_bandwidth, 'Bandwidth (Hz):', eng_widget, float)
            self._shrink(self._bww)
            self.top_layout.addWidget(self._bww)

        ##################################################
        # Sample rate controls
        ##################################################
        self._add_section("Sample Rate", self.top_layout)

        r = self.src.get_sample_rates()
        self._srr = Range(r.start(), r.stop(), r.step() or (r.stop() - r.start())/100, self.src.get_sample_rate(), 100)
        self._srw = RangeWidget(self._srr, self.set_sample_rate, 'Sample Rate (Hz)', eng_widget, float)
        self._shrink(self._srw)
        self.top_layout.addWidget(self._srw)

        ##################################################
        # File recording controls
        ##################################################

        self._add_section("File recording", self.top_layout)

        wid = Qt.QWidget()

        layout = Qt.QHBoxLayout()
        layout.setContentsMargins(0, 0, 0, 0)

        self._frl = Qt.QLabel('File Name')
        layout.addWidget(self._frl)

        self._fre = Qt.QLineEdit()
        layout.addWidget(self._fre)

        self._frb = Qt.QPushButton('REC')
        layout.addWidget(self._frb)

        wid.setLayout(layout)
        self.top_layout.addWidget(wid)

        self.recording = 0
        def record_callback():
            self.recording = 1-self.recording
            if self.recording:
                self._srw.setDisabled(True)
                self._fre.setDisabled(True)
                self._frb.setText('STOP')

                self.rec_file_name = self.record_to_filename()

                print("Recording samples to ", self.rec_file_name)
                self.file_sink.open(self.rec_file_name);
            else:
                self._srw.setDisabled(False)
                self._fre.setDisabled(False)
                self._frb.setText('REC')

                self.file_sink.close()
                print("Finished recording to", self.rec_file_name)

        self._fre.returnPressed.connect(record_callback)
        self._frb.clicked.connect(record_callback)

        ##################################################
        # DC Offset controls
        ##################################################

        if self.dc_offset_mode != None:
            self._add_section("DC Offset Correction", self.top_layout)

            wid = Qt.QWidget()

            layout = Qt.QHBoxLayout()
            layout.setContentsMargins(0, 0, 0, 0)

            self._dcb = self._chooser(["Off", "Manual", "Auto"], self.set_dc_offset_mode, self.dc_offset_mode)
            layout.addWidget(self._dcb)

            self._dcrr = Range(-1, +1, 0.001, 0, 20)
            self._dcrw = RangeWidget(self._dcrr, self.set_dc_offset_real, 'Real', "counter_slider", float)
            self._shrink(self._dcrw)
            layout.addWidget(self._dcrw)

            self._dcir = Range(-1, +1, 0.001, 0, 20)
            self._dciw = RangeWidget(self._dcrr, self.set_dc_offset_imag, 'Imag', "counter_slider", float)
            self._shrink(self._dciw)
            layout.addWidget(self._dciw)

            wid.setLayout(layout)
            self.top_layout.addWidget(wid)

        ##################################################
        # IQ Imbalance controls
        ##################################################

        if self.iq_balance_mode != None:
            self._add_section("IQ Imbalance Correction", self.top_layout)

            wid = Qt.QWidget()

            layout = Qt.QHBoxLayout()
            layout.setContentsMargins(0, 0, 0, 0)

            self._iqb = self._chooser(["Off", "Manual", "Auto"], self.set_dc_offset_mode, self.iq_balance_mode)
            layout.addWidget(self._iqb)

            self._iqmr = Range(-1, +1, 0.001, 0, 20)
            self._iqmw = RangeWidget(self._iqmr, self.set_iq_balance_mag, 'Mag', "counter_slider", float)
            self._shrink(self._iqmw)
            layout.addWidget(self._iqmw)

            self._iqpr = Range(-1, +1, 0.001, 0, 20)
            self._iqpw = RangeWidget(self._iqpr, self.set_iq_balance_pha, 'Pha', "counter_slider", float)
            self._shrink(self._iqpw)
            layout.addWidget(self._iqpw)

            wid.setLayout(layout)
            self.top_layout.addWidget(wid)

    def set_dc_offset_mode(self, dc_offset_mode):
        if dc_offset_mode == 1:
            self._dcrw.setDisabled(False)
            self._dciw.setDisabled(False)

            self.set_dc_offset()
        else:
            self._dcrw.setDisabled(True)
            self._dciw.setDisabled(True)

        self.dc_offset_mode = dc_offset_mode
        self.src.set_dc_offset_mode(dc_offset_mode)

    def set_dc_offset_real(self, value):
        self.dc_offset_real = value
        self.set_dc_offset()

    def set_dc_offset_imag(self, value):
        self.dc_offset_imag = value
        self.set_dc_offset()

    def set_dc_offset(self):
        correction = complex(self.dc_offset_real, self.dc_offset_imag)

        try:
            self.src.set_dc_offset(correction)

            if self._verbose:
                print("Set DC offset to", correction)
        except RuntimeError as ex:
            print(ex)

    def set_iq_balance_mode(self, iq_balance_mode):
        if iq_balance_mode == 1:
            self._iqpw.setDisabled(False)
            self._iqmw.setDisabled(False)

            self.set_iq_balance()
        else:
            self._iqpw.setDisabled(True)
            self._iqmw.setDisabled(True)

        self.iq_balance_mode = iq_balance_mode
        self.src.set_iq_balance_mode(iq_balance_mode)

    def set_iq_balance_mag(self, value):
        self.iq_balance_mag = value
        self.set_iq_balance()

    def set_iq_balance_pha(self, value):
        self.iq_balance_pha = value
        self.set_iq_balance()

    def set_iq_balance(self):
        correction = complex(self.iq_balance_mag, self.iq_balance_pha)

        try:
            self.src.set_iq_balance(correction)

            if self._verbose:
                print("Set IQ balance to", correction)
        except RuntimeError as ex:
            print(ex)

    def set_sample_rate(self, samp_rate):
        samp_rate = self.src.set_sample_rate(samp_rate)
        if hasattr(self.scope, 'set_frequency_range'):
            self.scope.set_frequency_range(self.src.get_center_freq(), samp_rate)
        if hasattr(self.scope, 'set_sample_rate'):
            self.scope.set_sample_rate(samp_rate)
        if self._verbose:
            print("Set sample rate to:", samp_rate)

        try:
            if hasattr(self._bww.d_widget, 'setValue'):
                self._bww.d_widget.setValue(samp_rate)
            else:
                self._bww.d_widget.counter.setValue(samp_rate)
        except (RuntimeError, AttributeError):
            pass

        return samp_rate

    def set_named_gain(self, gain, name):
        if self._verbose:
            print("Trying to set " + name + " gain to:", gain)

        gain = self.src.set_gain(gain, name)
        if self._verbose:
            print("Set " + name + " gain to:", gain)

    def set_bandwidth(self, bw):
        if self._verbose:
            print("Trying to set bandwidth to:", bw)
        clipped_bw = self.src.get_bandwidth_range().clip(bw)
        if self._verbose:
            print("Clipping bandwidth to:", clipped_bw)
        if self.src.get_bandwidth() != clipped_bw:
            bw = self.src.set_bandwidth(clipped_bw)

            if self._verbose:
                print("Set bandwidth to:", bw)

        return bw

    def set_freq(self, freq):

        freq = self.src.set_center_freq(freq)

        if hasattr(self.scope, 'set_frequency_range'):
            self.scope.set_frequency_range(freq, self.src.get_sample_rate())
        if hasattr(self.scope, 'set_baseband_freq'):
            self.scope.set_baseband_freq(freq)

        try:
            if hasattr(self._fw.d_widget, 'setValue'):
                self._fw.d_widget.setValue(freq)
            else:
                self._fw.d_widget.counter.setValue(freq)
        except (RuntimeError, AttributeError):
            pass

        if freq is not None:
            if self._verbose:
                print("Set center frequency to %.10g"%freq)
        elif self._verbose:
            print("Failed to set freq.")
        return freq

    def set_freq_corr(self, ppm):
        self.ppm = self.src.set_freq_corr(ppm)
        if self._verbose:
            print("Set frequency correction to:", self.ppm)


def main():
    qapp = Qt.QApplication(sys.argv)

    tb = app_top_block(qapp.arguments(), "osmocom Spectrum Browser")
    tb.start()
    tb.show()

    def sig_handler(sig=None, frame=None):
        print("caught signal")
        Qt.QApplication.quit()

    signal.signal(signal.SIGINT, sig_handler)
    signal.signal(signal.SIGTERM, sig_handler)

    # this timer is necessary for signals (^C) to work
    timer = Qt.QTimer()
    timer.start(500)
    timer.timeout.connect(lambda: None)

    def quitting():
        tb.stop()
        tb.wait()
    qapp.aboutToQuit.connect(quitting)
    qapp.exec_()


if __name__ == '__main__':
    main()
